The present invention relates to improvements in heat sinks for electronic semiconductor devices, especially so-called plastic power devices having both metallic tabs and plastic-encapsulated semiconductor packages, and, in one particular aspect, to novel and improved resilient one-piece sheet-metal heat-dissipating attachments for miniature plastic power devices which are of economical manufacture and may be readily mounted in place as self-holding heat sinks making intimate broad-area thermally-conductive contacts and exhibiting relatively large radiating surfaces and ample air-circulation channels.
As is well known, applications of small-size electronic semiconductor devices and circuit modules are severely limited in respect of the self-generated heat which they can successfully expel and prevent from building up as they are called upon to operate at higher and higher powers. In some instances, the environments of use permit elaborate forced-liquid cooling systems to be employed, but a very common and economical expedient instead involves the attachment of small finned metal extrusions or stampings which help to conduct and radiate heat away from the thermally-vulnerable regions. To further the latter purposes, encapsulated semiconductor devices or packages are sometimes provided with exposed heat-transfer parts, such as relatively thick metal tabs or plates, which promote thermal-energy transfer to such attachments and, in turn, to the ambient environment. The heat-dissipating attachments intended for use with such heat-transfer parts may include a resilient spring-clip member cooperating with a heat-dissipating base (as in U.S. Pat. Nos. 3,548,927 and 4,054,901), or such attachments may take the form of the single stamped sheet-metal body shaped both to promote cooling and to hold itself in place (U.S. Pat. Nos. 3,893,161 and 4,012,769 and 4,041,524).
Ease and convenience of fitting heat-sink attachments are important factors, as are, also, the creation and maintenance of broad-area efficient and effective heat-exchange paths for both conductive and convective modes of cooling. However, when auxiliary fasteners and tools must be used, the fastening operations can become quite awkward, and, when self-clipping arrangements are exploited instead, their designs may permit only small-area contacting to occur where one would prefer to develop broader areas for maximum heat-transfer. If intimate tightly-sprung broad-area regions of clamping are designed into a heat sink, it may then be difficult to force it into place and to avoid damage both to the device, which may itself be rather small and delicate, and to its frail leads. In accordance with the present teachings, such difficulties are reduced by way of heat-sink attachments which may be fabricated inexpensively and with good utilization of sheet metal stock which is stamped and bent to a trough-like body having intergral fingers which spring inwardly from along a slotted side to engage and hold a plastic semiconductor package inside it and in good contact with its inner surfaces, and in which the slot margins merge with a pair of broad-area fins spread and spaced to transfer heat away from the body.